Signal for trunk-lines.



UNITED STATES PATENT OFFICE.

FRANK R. MCBERTY, OF DOWNERS GROVE, AND JAMES L. MCQUARRIE, OF CHICAGO,ILLINOIS, ASSIGNORS TO THE WESTERN ELECTRIC COMPANY,

or CHICAGO, ILLINOIS.

SIGNAL FOR TRUNK-LINES.

SPECIFICATION forming' part of Letters Patent N o. 667,448, datedFebruary 5, 1901.

Annlioation filed January 1l, 1897. Serial No. 618,790. (No model.)

T0 (L7/Z whom t may concern.-

Be it known that we, FRANK R. MOBERTY, residing at Downers Grove, in thecounty of Du Page, and JAMES L. MCQUARRIE, residing atChicago, in thecounty of Cook, State of Illinois.citizens of the United States,haveinvented a certain new and useful Improvement in Signals forTrunk-Lines, (Case No. 51,) of which the lollowingis afull,clear,concise, and exact description, reference being had to theaccompanying drawing, forming a part of this specification.

Onrin vention refers to trunk-lines between different switchboards of atelephone eX- change; and it consists in certain signals to apprise eachof the operators of acts performed by the other and by the subscriberand means for operating the signals automatically in the process ofmaking connection between Stations.

The invention is particularly useful in connection with tru uli-linesextending between a switchboard whereon subscribers lines terminate andanother whereon special toll-lines or other similar circuits terminate.It is further designed for association with subscribers lines litt-edwith signals responding automatically to movements of the telephone atthe substation in ils use or disuse.

The following steps are commonly followed in establishing connectionbetween the terminal of a subscribe1"s line in the subscribersswitchboard and that of a toll-line in the tollswitchboard: Upon a callfrom the toll-line the operator at the toll-switchboard inserts one plugof a pair into the terminal socket of tne toll-line and the other intothe terminal socket of a trunk-line ending in a plug before au operator,to whom the terminal of the required subscribers line is accessible, atthe same time instructing the latter operator to complete the connectionbetween the trunkline and the required subscribers line. This acthaving' been performed, the two lines are united in a complete circuit.When the conversation has been completed,a suitably-operated signalindicates this fact t0 the toll operator, who thereupon removes theconnection between the toll-line and the trunk-line, after which thesubscribers operator must remove the connection between the trunk-lineand the subscribers line. Our invention provides means for automaticallyoperating the signals to instruct the operators when to perform t'neselatter act-s. The signals comprise a lamp before the toll operator,which is controlled by a relay responsive t0 currents in the subscribersline, determined by the position ofthe telephone-switch at thesnbscribers station, and a lamp before the subscribers operator,displayed consequent upon the act of withdrawing the plug from theterminal socket of the trunk-line at the toll-board.

The invention further provides a repeatingcoil to sever the conductiveconnection between the subscriber-s line and the toll-line, a switch forremoving the repeating-coil from the circuit in special cases, and adevice operated by that switch to prevent the display of the signalcontrolled by the relay when the latter is thus rendered inoperative.

The invention involves also certain details ofconstruction whereby thesystem is simplifled, which will be pointed out particularly in theclaims.

Our new system of signals is illustrated in theaccompanyingdrawing.Thereintwosubstations, one of which may be a subscribers station, arerepresented with lines terminating in suitable appliances in differentswitchboards, a trunk-line extending between the switchboards, and theusual connecting-plugs at one of them.

The apparatus at the snbscribers station A comprises atransmitting-telephone b and a receiving-telephone b', a signal-bell b2,and a switch b3 for bringing the appliances into connection with theline-circuit when the receiving-telephone is removed from theswitchhook. The line conductors are led to a springjack c in thesubscribers switchboard and thence through the magnet-windings of asignal-controlling relay d to a source of signaling-current e. Thesnbscribers signaling appliances in the switchboard are not shown infull, since they do not enter into the operation of thepresentinvention. The spring-jack is arranged to sever the line-circuitfrom these appliances when a plug is inserted into the jack. Theapparatus at station A may be of IOO difterent character, being adaptedfor magneto-call service. In addition to the telephone and theswitch-hook before described the station is furnished with a generatorb4 of alternating current for calling the central station. This linealso is connected with a spring -jack (designated f) in the switchboardand with an annunciator g, which is disconnected from the line when aplug is inserted into the spring-jack. The spring-jack c and signalinginstrument d of the subscribers line A maybe located in a subscribersswitchboard h. The corresponding appliances of the line A', which maybea toll-line, are located in a toll-switchboard h. Between theseswitchboards extends a trunk-line 5 6, which terminates in a spring-jackt' near the toll-switchboard and in a plug t" in the subscribersswitchboard. The operator at the toll-board is provided with the usualpairs of plugs k and k',with their pl iig-circuit for uniting thetoll-line and the trunk-line. Associated with the conductors of thetrunk-line is a signaling-conductor 9, forming part of asignaling-circuit between the switchboards h and h. This conductorterminates at springjack 1l in a thimble Z and in the plug 1l' in asleeve Z', adapted to make connection with thc thimble of a subscribersjack, into which it may be inserted. This thimble of the subscribersjack (designated Z2) is connected to earth through a conductor 10,including a resistance-coil m. This earth branch from the thimble ofvthe jack of the subscribers line may form a portion of thesignaling-circuits pertaining to the subscribers line. The plug 7o' atthe toll-board h is also furnished with a sleeve Z3, which is adapted toregister with the sleeve Z of spring-jack when the plug is inserted intothe spring-jack. The sleeve Z3 of plug le is connected by a conductor 11with the free pole of a grounded battery n. This .conductor includes asignal-lamp 0 and another battery p of similar polarity in the circuitto that of battery fn. A shunt 13 is arranged about the lamp-signal o,controlled by a relay q, connected with the circuit of plugs 7c k in away which will be presently be described. This shunt includes a smallresistance-coil r. The sleeve Z of plug t" is connected with the freepole of the same battery n by a conductor 12, which includes asignal-lamp o, associated with the plug i in the switchboard h.

The resistance m should be so adjusted with relation to the resistancesof lamps o and o' and the electromotive force of batteryn that when thecircuit through both lamps is closed neither shall receive currentsufcient to illuminate it, the eect of batteryp in the conductor 1lbeing for the present disregarded. Under such a condition theinterruption of conductor 11 or its disjunction from the conductor 9 ofthe trunk-line signaling-circuit will cause the diversion of the entirecurrent from battery n through the lamp o', whereby this lamp willbecome lighted. Then in this circuit, the circuit 9 11 being` closed,the battery p should have such an electromotive force as to cause theillumination of lamp o, while assisting in the extinction of lamp o'.The resistance r should be sufficient to permit the extinction of lamp 0when the cond uctor 13 is closed at the switch-contacts of the relay. Itmay have a resistance approximately equal to that ot the lamp. Suitableelectrical dimensions for these diierent appliances may be as follows:The battery n may be of twenty volts, the battery p of four volts, thelamps o and o may be four-volt lamps, taking two-tenths yampere each,the resistance m may be forty ohms, and resistance fr twenty ohms.

The operators plugs at the toll-board h are connected togetherinductively through the medium of a repeating-coil .9,thelne-contacts ofplug Zt being connected together by conductors 14 and 15 through onewinding s of the repeating-coil and the similar contactpieces of plug labeing connected together by other conductors 16 and 17 through a dividedwinding s2, between whose portions a' source of currentt isinterposed.The usual callingkey uis provided for connecting a generator ofcalling-current with key 7c and also a listening-key fu for connectingthe operators telephone with the circuit. In addition to these usualkeys is a special key w, whose switchcontacts are interposed in theconductors 14 15 16 17. These switch-contacts are so arranged that inthe normal position ot' the key the circuits are as before traced, whilein the alternate or occasional position of the key conductors 14: and 16and conductors 15 and 17 are brought into conductive connection,respectively, the windings s s2 of the repeating-coil being disconnectedfrom the circuit. This key is designed for use only when it is desiredthat the connection made through the plugs shall be free from localgrounds and unnecessary appliances, as in long-distance connections orin circuits subject to disturbances which makes conversation difficult.

The magnet of relay q is connected in paral-` lelwith one of thewindings s2 of the repeating-coil, so as to share with it any currentwhich may ow from battery t through the plug Zr. and the line with whichit may be temporarily associated. The key w carries two switch-contacts'w' and wz, which become closed together when the key is thrown intoposition to disconnect the windings of the repeating-coil from theplugs. One of these contact-points is connected with one pole of batteryt and the other with one terminal of the relay q in such a way that apath for current from battery t is provided through relay IOO IIO

q when the key is thrown into position to dishave the usual instructionor order circuit 16 between their telephones to permit them tocommunicate orders orally.

ln tracing the operation of this system of signals assume that aconnection is required from station A to stat-ion A. The operation ofthe station-generator at the former station causes the display of theline-annunciator g, whereupon the operator at the toll-board 71 insertsplug la into spring-jack f, brings her telephone into connection withthe plug-circuit 14 16 15 17 by means of keyc, and learns the order forthe required connection. She then requests the operator at board h bymeans of the order-wire to connect the trunkline 5 6 with the requiredsubscribers line before the latter operator. At the time of gi ving thisinstruction to the operator at board 7L the operator at toll-board hinserts plug k into the spring-jack t' of the trunk-line. Subsequentlythe operator at board 71, complying with the instruction,inserts plug t"into the spring-jack c of the required line. This completes a circuitfrom battery t at the tollboard through conductors 16 and 17 of theplug-circuit, conductors 5 and 6 of the trunkcircuit, and line-wires 1and 2 of the line to the substation. pletes a circuit from battery 'nthrough wires 11, 9, and 10, including battery p, in which currentcirculates sufficient to illuminate the supervisory lamp 0 at thetoll-board. As before stated, the electrical conditions of the circuitformed are such that the difference of potential between the terminalsof lamp o is insufficient to cause the lighting of that lamp. Since thecircuit of the line atthe called substation is practically open to acurrent from battery t, the relay q remains inert and permits theillumination of. supervisory lamp o. Hence the displayed condition ofthis lamp indicates to the toll-operator the condition of the telephonesat the substation A. The lighting of the lamp also signifies thecompletion of the local circuit traced, and hence assures her that theoperator at board h has completed the connection with the subscribersline.' The operator at the toll-board now sends a calling-current to thestation A b'y means of calling-key u. The response of the calledsubscriber is signalized by the extinction of supervisory lamp o, thisbeing accomplished through the excitement of relay q by current frombattery t in the line. As before mentioned` if the connection betweenstations A and A' be of high resistance or peculiarly subject todisturbances the operator at board h' may now withdraw therepeating-coil s from the circuit, supervising the connection by meansof her listening-key i: only. The interruption of current from batterytthrough relay q to the station A by the severance of connection betweenthe plug-circuit and the repeating-coil would tend to permit the displayof supervisory signal o; but the local closed circuit which is formedthrough the relay q would prevent such condition. Or-

At the same time it comdinarily, however, the operator leaves therepeating-coil in connection with the plug-circuit. Hence when thetelephone at station A is replaced upon its switch at the termination ofconversation supervisory signal 0 becomes displayed. This constitutes asignal for disconnection. Accordingly the operator at board 71,withdraws plugs k and k from the spring-jacks into which theyareinserted. The act of withdrawing plug 7c from spring-jack t' breaks theconnection beween conductors 11 and 9, and thus removes the cause of theslight difference of potential between the terminals of lamp 0. Thislamp therefore receives the full current from batteryn throughconductors l2 and 10, whereby the lamp is lighted. Its illuminationconstitutes a signal to the operator at board h to remove theconnection, and she accordingly replaces the apparatus in its normalcondition.

We claim as new- 1. The combination with two telephonelines andspring-jacks thereof, plugs in the spring-jacks and a plug-circuituniting the lines, of a source of current included in the circuit andmeans for closing the line-circuit at the substation during the use ofthe telephone, a magnet interposed in the circuit to respond to currenttherein, and a supervisory signal controlled by the magnet, adapted tobe displayed when the magnet is inert, a key constructed to disconnectthe said source of current from the plug-circuit when in one position,and switch-contacts associated with the key adapted io alter the circuitdetermining the display of the supervisory signal to prevent the displaythereof, as described.

2. The combination with two telephonelines, one of which is providedwith a switch to close the line-circuit during the use of the telephone,spring-jacks for the lines, plugs in the spring-jacks, and aplug-circuit uniting the plugs, of a repeating-coil having its windingsnormally interposed in the plugcircuit, a source of current in a bridgeof the plug-circuit between said windings, a relay connected with theplug-circuit to respond to current therein from. the said source, alocal circuit including a supervisory signal-lamp, and a shunt of thelamp adapted to be closed by the switch-contacts of the relay when therelay is inert, a key constructed to disconnect the repeating-coil fromthe plug-circuit and to complete the connection between the plugsdirectly, and switch-contacts adapted to close a local circuit through awinding of the relay when the said key is brought into position to cutout the repeating-coil, as described.

3. The combination with a telephone-line extending in two limbs from asubstation to a central office, of a spring-jack for the line at thecentral office, a plug adapted for insertion in the spring-jack to makeconnection with the line, a plug-circuit having a pair of conductorsadapted to loe` connected with the two limbs of the telephone-line byway of the IOO IIO

plug and spring-jack, a source of current in a bridge of theplug-circuit conductors, a relay in the plug-circuit responsive tocurrent therein, and a switch at the substation for controlling the tlowof current from said source through the plugcircuit and telephone-line,a supervisory signal associated with the plug-circuit, a local circuitincluding said supervisory signal, closed in registering contacts of theplug and spring-jack, and a shunt about said supervisory signalcontrolled by the relay, substantially as described. v

4. The combination with a telephone-line having a switch at thesubstation adapted to close the line during the use of the telephone, aspring-jack therefor, aplug in the springjack, and a plug-circuittherefor, a source of current in a bridge of the plug-circuit and arelayconnected with the plug-circuit to respond to current therein, of alocal circuit including a supervisory signal, a shunt about the saidsupervisory signal including a resistance-coil, said shunt beinginterrupted at the switch-contacts of the relay when the relay is inert,as described.

5. The combination in a circuit divided into two parallel branches,asource of current and a resistance-coil in the undivided portion of thecircuit, a signal-lampin each of said parallel branches, a source ofcurrent in one of vthe branches, and a switch controlling one of saidbranches, whereby one of the lamps may be extinguished, as described.

6. In combination in a circuit divided int-o two parallel branches, asource of current and a resistance-coil in the undivided portion of thecircuit, a signal lamp in each of the branches, a source of current anda switch in one of the branches, a shunt about the signal-lamp in thesaid branch and a switch controlling the shunt, as described.

7. The combination with a trunk-line and means for making connectionbetween each end thereof and a subscriber-s line, of a signal-circuitincluding a resistance-coil and a source of current, a signal in thecircuit at one terminal of said switchboard, a shuntcircuit about thesignal, and switch-contacts closing the shunt in the act of makingconnection with the other terminal of the trunkline, substantially asdescribed.

8. The combination with a trunk-line and means for making connectiontherewith at each terminal, of a signal-circuit, a source of current anda resistance-coil included there in, said signal-circuit being dividedinto parallel branches, a supervisory signal in each of said branches,the supervisory signals being located at the different ends of thetrunkline, switch-contacts adapted to close the signal-circuit whenconnection is made with one end of the trunk-line, and other switch-comtacts closed together in the act of making connection with the otherterminal of the trunkline, said last-mentioned switch-contacts beingincluded in the circuit with the signal at the same terminal, andasource of current in the branch with said last-mentioned signal,substantially as described.

9. The combination with telephone-lines provided with means for creatingcurrent in the lines during the use of the station-telephones, of atrunk-line for uniting the lines, a signal-circuit associated with thetrunkline including a source of current and a resistance-coil anddivided into two parallel branches, a supervisory signal in each of thebranches, the signals being located at different terminals of thetrunk-line, switch-contacts adapted to close the signal circuit throughregistering contacts brought into connection in uniting the trunk-linewith the subscriber-s line at one te rminal,other switchcontacts closedtogether in making connection with the other terminal of the trunklinecontrolling the branch including the supervisory signal at the sameterminal, a source of current in the last-'mentioned branch, a shuntabout the signal in the same branch, and a relay responsive to thecurrents determined by the display of the substation apparatus of thetelephone-line, substantially as described.

10. The combinationwith a telephoneline and means for making connectiontherewith at two or more points, of a local conductor forming part of acircuit including a source of current together with a resistance-coil,said local circuit being divided at one point into parallel branches,one of said branches being normally open, a signal-lamp in each of thebranches, registering contacts of a plug and spring-jack in the normallyopen branch, and a source of current in one of the branches, whereby theinsertion of the said plug in the spring-jack changes the current in thesignaldamp connected with the local conductor at the distant point, asdescribed.

In witness whereof we hereunto subscribe our names this 21st day ofNovember, A. D. 1896.

FRANK R. MCBERTY. JAMES L. MCQUARRIE.

Witnesses:

ELLA EDLER, DUNCAN E. WILLETT.

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